Opto 22 G4AD3 Data Sheet
I/O MODULES
ANALOG INPUT
G4
DAT A SHEET
Form 426-050809
Description
The G4AD3 module provides a single channel of transformer and optically isolated current-to-digital conversion. The nominal input
range is 4 to 20 milliamps with an under/over range capability from less than 3 milliamps to greater than 35 milliamps. One of the unique
features is that the isolated loop supply can be provided by the G4AD3. This eliminates the need for the user to provide the loop supply
(typically 15-48 V) and also saves the associated wiring, barrier strips, etc. The G4AD3 module also includes complete electrical channelto-channel isolation which eliminates any ground loop problems. Modules plug into an Opto 22 Modular controller or an analog I/O brick
and are secured by a captive screw. The field connections are made to the terminal strip located on the Brick base or controller I/O board.
NOTE: Any system using analog sensors and input modules should be calibrated annually for analog signals. To do so, use OptoControl
commands “Calculate and Set Analog Offset” and “Calculate and Set Analog Gain.”
Part
Number
G4AD3 4 To 20 mA Input
Description
page 1/4
I/O MODULES
ANALOG INPUT
G4
DAT A SHEET
Form 426-050809
Specifications
G4AD3 Specifications
Nominal inp ut range 4 to 20 mA
Module Input Impedance* 414 Ω∗
Over/under range 3 to 35 mA
Loop supply 28 VDC nominal
Accuracy** 16 µA**
Response time Full-scale step change in 3 ms
Resolution 12 bits
Iso la tion (Transi ent)
Input-to-output
Input-to-analog supply
Ambient temperature
Operating
Storage
4,000 V
4,000 V
-30° C to 70° C
-40° C to 85 ° C
rms
rms
page 2/4
* This is the equivalent impedance for the G4AD3 at full scale (20mA). The equivalent impedance is calculated by using the following
formula:
Equivalent impedance = 249 Ω + 3.3V/0.02A = 414 Ω
The module has an internal resistance of 249 Ω in series with a 3.3V zener diode.
It is not possible to use an ohm-meter to accurately measure the impedance across the field terminals of the G4AD3. This is because
ohm-meters typically supply only 1 volt excitation which is not sufficient to cause current to flow through the 3.3V zener diode. Therefore,
the ohm-meter will display infinite impedance (i.e. Mega-ohms, or an open circuit).
In certain applications the total loop impedance may exceed the maximum impedance that the loop transmitter can drive to full scale
(20mA). This may be the case in applications using intrinsic safety barriers. An alternate approach is to use the 0 to 5 volt G4AD6 (or
G4AD6HS) with a 250 Ω precision resistor (Dale type RN is recommended) across the input terminals. This will provide a 1 volt input at
4mA and a 5 volt input at 20mA.
** Accuracy figure requires use of gain and offset commands.
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